Conventionally, a movable tray on which sheets discharged from a sheet discharge port of an image forming apparatus body or finisher are stacked is known. The movable tray sequentially descends according to the number of sheets discharged from the sheet discharge port and moves downward to a predetermined lower limit position so that the quantity of sheets stacked on the movable tray reaches the maximum.
However, when an object such as luggage that prevents the descent of the movable tray exists below the movable tray, the downward movement of the movable tray may become disturbed by the luggage and the movable tray may not be able to move to the predetermined lower limit position.
As the movement of the movable tray is thus disturbed, an error occurs and the discharge of sheets is suspended.
Then, the discharge of sheets cannot be resumed until the luggage or the like causing the occurrence of the error is eliminated from below the movable tray.